Physical Chemical Properties of Fermented and Roasted Rambutan Seed Fat (RSF) as A Potential Source of Cocoa Butter Replacer

Abstract

Rambutan (Nephelium opossum L) is one of the most important tropical fruits that is originally found in Malaysia, Thailand, the Philippines, Vietnam, Borneo and other countries in this region. The industrial processing of this fruit produces seeds and peels as waste materials. The aim of this work was to determine the physical-chemical properties of fermented-roasted Rambutan seed fat (RSF) and its mixtures with Cocoa butter (CB) in term of viscosity, texture (hardness), thermal stability, and fatty acid composition, and free fatty acid, acid value. The mixtures M3, M4, and RSF which possess similar crystal formation showed almost similar hardness index in the range of 11.18 to 24.77. The mixtures M1 and CB exhibited higher hardness index than M2, M3, M4 and RSF in the range of 57.55 to 63.85. The results showed that a low viscosity was observed in the mixture CB and M1 with increasing the temperatures at 35, 40 and 50 oC whereas, a high viscosity was observed in the other mixture such as M3, M4, and RSF with increasing the temperature, respectively. The result found that the major fatty acid composition was present in CB (100%CB+0%RSF) and M1 (80%CB+20%RSF), such as palmitic, stearic and oleic acid, respectively. The results showed no significant differences (P > 0.05) in FFA among CB (2.72±0.65%), M1 (3.01±0.32%) and M2 (3.47±0.16%). At the same time, the results of A.V showed significant differences (P < 0.05) among CB (4.68±1.29), M1 (5.98±0.64) and M2 (6.92±0.33) mgKOH/g, respectively, but M1 value was very close to CB value. The results exhibited that CB and M1 had a lower viscosity than M2, M3, M4 and RSF with increasing temperature. From these results, it was found that it is possible to utilize rambutan seed fat as a cocoa butter replacer in a suitable ratio depending on the final products.

Full text

Vol.
7
(201
7
) No.
1
ISSN: 2088
-
5334
Physical Chemical Properties of Fermented and Roasted Rambutan
Seed Fat (RSF) as A Potential Source of Cocoa Butter Replacer
Luma Khairy.H#,*, Fered Saadoon#,%, Boshra Varastegani#, Tajul A. Yang#, Wahidu Zzaman#,&
#Food Technology, School of Industrial Technology, University Sains Malaysia, Minden 11800 Pulau Pinang Malaysia
E-mail: taris@usm.my
*Department of Food Science, School of Agriculture, University of Baghdad, Baghdad- Iraq
Email: luma_khairy@yahoo.com
%Department of Quality control, General Company for Grain Processing, Ministry of trade, Baghdad, Iraq
E-mail: feredabuaimen@yahoo.com
&Department of Food Engineering and Tea Technology, Shahjalal University of Science and Technology, Sylhet-3114, Bangladesh
Corresponding author Email: wahidaft@yahoo.com
Abstract— Rambutan (Nephelium opossum L) is one of the most important tropical fruits that is originally found in Malaysia,
Thailand, the Philippines, Vietnam, Borneo and other countries in this region. The industrial processing of this fruit produces seeds
and peels as waste materials. The aim of this work was to determine the physical-chemical properties of fermented-roasted Rambutan
seed fat (RSF) and its mixtures with Cocoa butter (CB) in term of viscosity, texture (hardness), thermal stability, and fatty acid
composition, and free fatty acid, acid value. The mixtures M3, M4, and RSF which possess similar crystal formation showed almost
similar hardness index in the range of 11.18 to 24.77. The mixtures M1 and CB exhibited higher hardness index than M2, M3, M4 and
RSF in the range of 57.55 to 63.85. The results showed that a low viscosity was observed in the mixture CB and M1 with increasing
the temperatures at 35, 40 and 50 oC whereas, a high viscosity was observed in the other mixture such as M3, M4, and RSF with
increasing the temperature, respectively. The result found that the major fatty acid composition was present in CB
(100%CB+0%RSF) and M1 (80%CB+20%RSF), such as palmitic, stearic and oleic acid, respectively. The results showed no
significant differences (P > 0.05) in FFA among CB (2.72±0.65%), M1 (3.01±0.32%) and M2 (3.47±0.16%). At the same time, the
results of A.V showed significant differences (P < 0.05) among CB (4.68±1.29), M1 (5.98±0.64) and M2 (6.92±0.33) mgKOH/g,
respectively, but M1 value was very close to CB value. The results exhibited that CB and M1 had a lower viscosity than M2, M3, M4
and RSF with increasing temperature. From these results, it was found that it is possible to utilize rambutan seed fat as a cocoa butter
replacer in a suitable ratio depending on the final products.
Keywords— rambutan seed; cocoa butter; texture; thermal stability; fatty acid composition
I. INTRODUCTION
Fats are used as main ingredients in food, cosmetic, and
pharmaceutical products [1]. The crystallization of fats has
industrial applications when it is controlled; end products
such as chocolate, margarine, and whipped cream can be
obtained; the crystallization phenomenon of fats can be used
to isolate fats from natural resources [2]. Cocoa butter (CB)
is one of the natural fats, obtained from cocoa seeds
(Theobroma cacao); it is typically used as a major
component of chocolate and other confectionery products
because of its physical and chemical properties [3]. CB is
solid at room temperature (below 25 °C) and liquid at body
temperature (~37 °C); it consists mostly of palmitic (C16),
stearic (C18:0), and oleic acids. Virtually, all oleic acids are
esterified in the central position of all glycerol molecules
(Sn-2), whereas saturated fatty acids are typically located in
(Sn-1,3) positions. The composition and allocation of fatty
acids lead to a symmetrical triglyceride composition of CB
that is rich in 1,3-dipalmitoyl1-2-oleoyl-glycerol (pop) and
1-palmitoyl-3-stearoyl-2-oleoyl-glycerol (POS) [4]. This
triglyceride composition of CB is generally responsible for
its diverse crystalline polymorphic forms, while fatty acid
compositions are responsible for fat solidification in its
liquid state [5]. CB is known to be more expensive than
other vegetable fats because of its specific characteristics
57

and it is cultivated in only a few countries [6]. Therefore,
the food industry is keen to find other sources of fats as
alternatives to CB in producing chocolates for various
reasons, including economic [7]. CB alternatives are defined
as non-lauric fats that can replace CB either partially or
completely in chocolate or other food products. Lipp and
Anklam [8] previously mentioned that the utilization of
natural or processed lipids as cocoa butter alternative can be
decided using its compositional data (fatty acid composition
and triacylglycerol conformation) and thermal characteristics
such as crystallization and melting characteristic. This work
was intended to determine the physical properties of
fermented-roasted RSF and its mixtures with CB in viscosity,
texture (hardness), thermal stability, fatty acid composition,
free fatty acid, acid value to compare these mixtures with
CB and to determine the mixture which was more similar to
cocoa butter properties.
II. MATERIALS AND METHODS
A. Materials
CB was purchased from an Indonesian coffee company
and the Cocoa Research Institute, Jember, East Java,
Indonesia. Meanwhile, raw rambutan (Nepheliumlappaceum
L.) seeds were supplied by a rambutan canning industry in
Sungai Petani, Kedah, Malaysia.
B. Fermentation and Roasting of Rambutan Seeds
The fermentation process was performed on rambutan
seeds, which were still covered by small amounts of
rambutan pulp. The rambutan seeds were transferred into
plastic baskets (625 mm × 425 mm × 294 mm), which were
previously lined with banana leaves. After filling in the
baskets with raw rambutan seeds, the baskets were covered
with banana leaves for 6 days, with mixing every 3 days. On
the 6th day of fermentation, the banana leaves cover was
opened and the rambutan seeds inside the fermentation
container were stirred with a wood spatula. After the
fermentation time was sufficient, the dried rambutan seeds
were roasted at 150 °C for 30 minutes by oven-drying
(AFOS Mini Kiln, Hull, England). After roasting, the
samples were cooled at room temperature and stored until
the screw-pressing process for RSF production [9].
C. RSF Extraction
RSF extraction was performed using a KOMET screw oil
expeller DD 85 IG (IBG MonfortsOekotec GmbH & Co. KG,
Ger-many). Dried rambutan seeds were dehusked and heated
at 60 °C for 30 minutes by oven-drying (AFOS Mini Kiln,
Hull, England). The screw-pressing process produced RSF,
which was a viscous mixture of rambutan seed powder and
RSF. The separation of RSF from rambutan seed butter was
achieved through filtration under a heated condition (60 °C).
Afterward, the collected RSF was transferred into inert-
screw-cap bottles [9].
D. Preparation of RSF and Cocoa Butter Mixtures
Mixtures of rambutan seed fat and cocoa butter were
prepared following proportions as mentioned in Table 3.1.
The levels were in the range of 0% to 100% with the total
mixture was 100% (CB+RSF=1). The mixing process was
carried out by adding predetermined proportions (w/w) of
cocoa butter and rambutan seed fat.
TABLE I
PROPORTION OF THE RSF AND COCOA BUTTER
Mixtures of CB & RSF CB%
a
RSF%
b
Mixture 1 (CB) 100 0
Mixture 2 (M1) 80 20
Mixture 3 (M2) 60 40
Mixture 4 (M3) 40 60
Mixture 5 (M4) 20 80
Mixture 6 (RSF) 0 100
a CB% = proportion of cocoa butter, b RSF% = proportion of Rambutan seed
fat
CB was incorporated into RSF in six proportions, namely,
100/0, 80/20, 60/40, 40/60, 20/80, and 0/100 (w/w) CB to
RSF, as CB, M1, M2, M3, M4 and RSF respectively. Then,
the mixtures were melted in the oven (AFOS Mini Kiln, Hull,
England) at 60 °C for 15–20 minutes. The melted mixtures
were then homogenized using a vortex and transferred into
inert-screw-cap bottles and then stored at −4 °C until they
were used for analysis.
E. Texture Properties (Hardness Index)
Texture properties analysis was carried out using TA.XT
Plus texture analyzer (Stable Micro System, Ltd., UK)
following the method of Lannes et al. [10]. Cone probe was
utilized during this analysis and was set to penetrate the
samples with a constant speed of 2.0 mm/s for 10.0 mm. The
analysis was performed at 20˚C. The result of the analysis
was expressed as hardness diagram.
F. Thermal Stability Analysis
Thermal stability of RSF and CB mixture samples were
analyzed by means of thermal gravimetric analysis (TGA) in
nitrogen atmospheres employed TGA 4000 equipped with
C6 cooler (Perkin Elmer, Waltham, Massachusetts, USA).
The nitrogen flow rate was set at 50 ml/min at a heating rate
of 20˚C/min. Mass changes were recorded between 25 until
700 ˚C.
G. Viscosity Measurement
The viscosity was measured by use Viscometer Model
(SV-10 Japan). It was taken 45 ml of the sample and
transfers to Viscometer vial and then read the number of the
viscosity. Each value was taken triplicate at temperature 25
oC.
H. Fatty Acid Composition
Fatty acid methyl ester (FAME) was prepared according
to the method of Mondello et al. [11]. Melted samples (0.05
g) were transesterified in a Pyrex tube by using 2 ml of
borontrifluoride-methanol (20:80) reagent then heated for 30
min at 100°C in water bath. The heated solution was cooled
to room temperature. After cooling down, 2 ml of n-hexane
and 8 ml of distilled water were added to the mixture, which
was then mixed manually for 1 min and centrifuged at 3500
rpm for 2 minutes. Approximately 1 ml of the upper n-
hexane layer was transferred to a 1.5 ml glass insert for 2 ml
vials after diluting the extracted hexane to obtain a suitable
chromatographic response. Gas Chromatography (GC)
58

analysis was done using GC 2010 plus- FID (flame
ionization detector) (Shimadzu Corp., Nagakyo-ku, Kyoto,
Japan) equipped with SGE BPX70 (90% Cyanopropylphenyl
Polisiloxane, 0.32mm ID × 0.25μm × 30m) column (SGE
Analytical Science Pty Ltd, Victoria, Australia). The
condition of GC during the analysis was set as follows: The
injection port was set using split mode (split ratio = 1:10) at
temperature 250oC employed Helium (He) as carrier gas [11].
The column temperature was set at 70oC maintained for 1
min, then increasing to 150oC at 20o C/min ramp and then
increasing to 250oC at 10o C/min ramp. The final
temperature was maintained for 15 min. Fatty acids were
grouped as follows: saturated (SFA), mono (MUNA) and
poly (PUFA) fatty acids.
I. Analysis of Free Fatty Acid (FFA) and Acid Value (A.V)
The FFA was determined according to the method [12].
The first step was prepared 50 ml of alcohol by added in 2
ml phenolphthalein solution and 0.1 M sodium hydroxide
(NaOH) and produced a faint permanent pink. 7.05 grams of
melted fat sample were weighed into 250 ml conical flask
and mixed with prepared neutralized 50 ml of alcohol at first
step. Then, the mixture was titrated with 0.25 M sodium
hydroxide (NaOH) with a vigorous shaking until a
permanent faint pink developed. The volume of 0.25 sodium
hydroxide (NaOH) used in the titration steps was taken as
final read. The free fatty acid of the samples was expressed
as a percentage of oleic acid that was ml of 0.25 M sodium
hydroxide (NaOH) used in the titration of the sample. All
samples were measured in triplicate. The acid value of RSF
and its mixture with CB samples are correlated with free
fatty acid determination. FFA may also be expressed in
terms of acid value. The acid value of the samples was
calculated by the equation below:
A.V= percentage of fatty acid (as oleic) × 1.99 (1)
J. Statistical Analysis
Samples were carried out in triplicate and the data
analysis was using (ANOVA) followed by post hoc analysis,
Duncan multiple comparison analysis and all the data were
analysis using SPSS (Statistical Package for Social Science)
software version 20 (IBM Corporation, Armonk, New York
10504-1722 United State). The statistical analysis was
performed at 0.05 significant levels.
III. RESULTS AND DISCUSSION
A. Texture Properties (Hardness Index)
The differences in crystal formation of the mixtures
greatly affected their texture properties. As shown in Fig. 1,
the mixtures M3, M4 and RSF which possess similar crystal
formation showed almost similar hardness index in the range
of 11.18 to 24.77. The mixtures M1 and CB exhibited higher
hardness index than M2, M3, M4 and RSF in the range of
57.55 to 63.85. These results were agreed with Febrianto [9],
he found the hardness of the mixtures (RSF: CB) were lower
ranged from 21.32 to 27.91 compared to 56.34 in CB.
However, he showed a slightly different characteristic of
hardness in the mixture (90%CB/10%RSF) compared to
cocoa butter. Size and the distribution of crystal formation
may be the responsible factor for the difference between M2,
M3, M4 and RSF mixtures with M1 and CB. Smaller and
well-distributed crystal formation provides a higher hardness
index, whereas bigger crystal formation resulted otherwise.
Fig. 1 Changes in the hardness index of RSF and its mixtures with CB
B. Thermal Stability
The result of thermal stability analyses carried out on RSF
and its mixture with CB are shown in Table 2. The
decomposition temperature of M1 was more similar to CB, it
was observed in onset 344.39 and 394.59, mass loss rate
1.38 and 0.79, and the final decomposition temperature
521.14 and 616.06 of the M1 and CB, respectively. This
result indicated that CB and M1 were more resistant from
thermal decomposition than other mixtures. However, the
other mixtures showed different results; decomposition of
M2, M3, M4, and RSF started at 308.62, 306.75, 302.60 and
291.91, and ended at a lower temperature ranged around
489.89, 487.52, 485.85 and 482.83 than that of the CB and
M1 with the highest mass loss recorded at around 1.25 to
1.12%/˚C, respectively.
Previously, Lawler and Dimick [13] showed that cocoa
butter possessed the unique characteristic of polymorphism.
As mentioned in section 3.3.3; CB and M1 crystallized as β
form crystal, The β crystal formation possesses hard, but the
brittle texture of cocoa butter which is usually used for
storage and product development. This formation of the
crystal is also desirable due to its unique snap characteristic
and fast melting in the mouth feature. Therefore, CB and M1
were more resistant from thermal decomposition than the
mixture M2, M3, M4 and RSF, which crystallized in β and β'
form crystal. Nonetheless, similar to the thermal behavior
discussed in section 3.3.2; different thermal stability of RSF
compared to the CB may be also contributed by the TAG
composition.
C. Viscosity Measurement
The changes in physical properties of rambutan seed fat
and its mixture with cocoa butter during the roasting process
are considered a reliable guide to follow up the changes in
viscosity affected by different temperature.
59

TABLE II
TGA DEGRADATION POINT OF RSF AND ITS MIXTURE WITH CB
Sample
Degradation point (°C)
Onset
Max 1
Mass
loss
rate 1
(%/°C)
Max 2
Mass
loss
rate 2
(%/°C)
Offset
CB 394.59 431.69 0.22 522.12 0.79 616.06
M1 344.39 391.66 0.81 482.66 1.38 521.14
M2 308.62 338.53 0.87 432.92 1.25 489.89
M3 306.75 311.66 0.64 430.68 0.98 487.52
M4 302.60 307.96 0.71 429.53 1.12 485.85
RSF 291.91 306.39 0.52 425.01 1.12 482.83
The results of viscosity measurement are given in Fig. 2.
The results showed that a low viscosity was observed in the
mixture CB and M1 with increasing the temperatures at 35,
40 and 50 oC. whereas, a high viscosity was observed in the
other mixture such as M3, M4, and RSF with increasing the
temperature, respectively.4
Fig. 2 Changes in viscosity of RSF and its mixtures with CB at different
temperature
These results correspond with Zzaman et al. [14], he
suggested that mixture proportion up to 30% rambutan seed
fat had a higher viscosity than cocoa butter. Accordingly,
cocoa butter had a lower viscosity than rambutan seed fat,
which can be explained by type and long chain structure of
fatty acid and triacylglycerol composition [15]. According to
Lannes et al. [16] noted that characterized by the melting of
fat crystals is defined as the level of fat in a reticular
structure which are typically structured in the form of β’ that
conducted lead to higher viscosity more than β form
structure that given their smaller size, higher surface area
and potentially increased interfacial viscosity in emulsions.
D. Fatty Acid Composition
Cocoa butter contains many different lipids or fats.
According to Lannes and Gioielli [17] described that
primary triacylglycerols that combined with the cocoa butter
including; palmitic, stearic, and oleic fatty acids. Saturated
and unsaturated acids are obtained from many fats and lipids
combination of the fatty acids, which half of them are
heterogeneous. The fatty acid composition of all mixtures
was significantly different (p < 0.05) from one another as
shown in Table 3.
TABLE III
FATTY ACID COMPOSITION (% AREA) IN THE CB AND RSF MIXTURE
Fatty
acid
M1 M2 M3 M4
C8:0
1.13±0.02ᵉ 1.27±0.01ᵈ
1.41±0.01ᶜ 1.55±0.01ᵇ
C11:0
0.15±0.01ᵉ
0.30±0.01ᵈ
0.46±0.01ᶜ 0.61±0.01ᵇ
C12:0
15.69±0.01ᵇ
12.38±0.01ᶜ 9.08±0.01ᵈ
5.77±0.01ᵉ
C13:0
0.88±0.01ᵉ
1,76±0.01ᵈ
2.65±0.01ᶜ
3.53±0.01ᵇ
C14:0
0.63±0.01ᵉ 1.25±0.02ᵈ 1.87±0.01ᶜ
2.51±0.01ᵇ
C15:0 0.82±0.01ᵉ 1.65±0.01ᵈ
2.47±0.01ᶜ
3.31±0.01ᵇ
C16:0
22.14±0.01ᵇ
18.55±0.01ᶜ
14.97±0.01ᵈ
11.38±0.01ᵉ
C
16:1
2.65±0.01ᵉ
5.31±0.01ᵈ
7.94±0.01ᶜ
10.59±0.01ᵇ
C18:0 18.05±0.01ᵇ
15.56±0.01ᶜ
13.08±0.01ᵈ
10.57±0.02ᵉ
C18:1
cis 23.06±0.01ᵉ
23.68±0.01ᵈ
23.96±0.01ᶜ
24.91±0.01ᵇ
C18:1
trans 0.74±0.01ᵉ
1.47±0.01ᵈ
2.21±0.01ᶜ
2.94±0.01ᵇ
C18:2
trans 3.54±0.01ᵇ
2.65±0.01ᶜ
1.77±0.01ᵈ
0.88±0.01ᵉ
C18:3
2.72±0.01ᵇ
2.54±0.01ᶜ
2.38±0.01ᵈ
2.21±0.01ᵉ
C20:0
3.11±0.01ᵉ
6.21±0.01ᵈ
9.34±0.01ᶜ
12.45±0.01ᵇ
C20:1
0.65±0.01ᵉ
1.31±0.01ᵈ
1.94±0.01ᶜ
2.58±0.01ᵇ
C22:0
0.27±0.01ᵉ 0.54±0.01ᵈ 0.82±0.01ᶜ
1.08±0.01ᵇ
SFA 63.52 60.78 58.09 55.34
MUFA 26.45 30.46 34.11 38.44
PUFA 6.26 5.19 4.15 3.09
-GC analysis and expressed as % area.
-Different superscript letter on the same row represented
significantly different value (p<0.05).
The result found that the major fatty acid composition was
present in CB (100%CB+0%RSF) and M1
(80%CB+20%RSF), such as palmitic, stearic and oleic acid,
respectively. Whereas, two main fatty acid composition was
found in RSF, such as oleic and arachidic acid, add up to
almost 75%; present also are palmitic, stearic, gondoic,
palmitoleic, and behenic acids. The Palmitic acid in the RSF
was present in much smaller amounts (7.81%) than CB and
M1 (25.72%  22.14%); and stearic acid in RSF also showed
like a palmitic acid (8.11%, 20.53% and 18.05%),
respectively. The results showed that the oleic acid was
found in CB and M1 (22.44% and 23.06%) lower than RSF
(25.53%), respectively. The lauric acid content in CB and
M1 (18.99% and 15.69%) was higher than RSF (2.47%).
Moreover; Arachidic acid and other saturated fatty acid such
as gondoic and behenic acid found in RSF, but those fatty
acids were absent in cocoa butter, which may affect to high
melting point and high viscosity of rambutan seed fat [18]-
[19]. However, around 50% of the fatty acids in RSF is
saturated, including a high percentage of arachidic acid, a
fatty acid with a long chain and a relatively high melting
point. This composition gives RSF characteristic
physicochemical properties, thermal and phase behavior.
These results agree with Zzaman et al. [14] they founded
that lauric, palmitic, and stearic fatty acid in rambutan seed
fat were less than cocoa butter, but oleic acid found almost
the same. On the other hand, these results are quite different
compared with Sirisompong et al. [20] reported that RSF is
composed of 36.79% of oleic acid, 34.32% arachidic acid
and 4.69% palmitic acid. However, the differences in these
fatty acid proportions have also been reported previously; in
which, the differences in cultivar and plantation area was
suspected to be the most influencing factors. The increase of
60

oleic acid in CB and RSF sample during fermentation was
previously mentioned by Teng et al. [21], who found that the
increase of lipase activity during fermentation using
Rhizopus spp resulted the formation of oleic acid.
Meanwhile, the specific microorganism such as R.
oligosporus could utilize the fatty acids in lipid body, mainly
palmitic and stearic acid to support their cell wall
phospholipid development, resulting in the decrease of
palmitic and stearic acid in RSF. Moreover,
Sudaryatiningsih and Supyani [22] mentioned that PUFA
such as linoleic and linolenic acid could be generated by
converting oleic acid with desaturase enzymes.
E. Analysis of Free Fatty Acid (FFA) and Acid Value (A.V)
The free fatty acid (FFA) and acid value (A.V) in cocoa
butter and the mixtures with rambutan seed fat under study
were in (Table 4). The results showed no significant
differences (P > 0.05) in FFA among CB (2.72±0.65%), M1
(3.01±0.32%) and M2 (3.47±0.16%). At the same time, the
results of A.V showed significant differences (P < 0.05)
among CB (4.68±1.29), M1 (5.98±0.64) and M2 (6.92±0.33)
mgKOH/g, respectively, but M1 value was very close to CB
value.
TABLE IIV
ANALYSIS OF FREE FATTY ACID AND ACID VALUE IN RSF
Samples FFA
(% oleic acid) A.V
(mgKOH/g)
CB
(100%CB+0%RSF) 2.72±0.65c 4.68±1.29d
M1
(80%CB+20%RSF) 3.01±0.32c 5.98±0.64cd
M2
(60%CB+40%RSF) 3.47±0.16c 6.92±0.33c
M3
(40%CB+60%RSF) 4.89±0.81b 9.73±1.61b
M4
(20%CB+80%RSF) 6.49±0.00a 12.91±0.00a
RSF
(0%CB+100%RSF) 6.86±0.16a 13.66±0.23a
-Values are mean ± standard deviation of three replications.
-Different superscript letter on the same row represented
significantly different value (p<0.05).
These differences in free fatty acid and acid value
between CB, M1, and M2 were small, some sample had a
higher content, others had a lower content of Diacylglycerols
(DAGs). Diacylglycerols are important because they retard
the phase transformation from β’ to β, this can negatively
influence the cooling curve and thus be a disadvantage for
the tempering of chocolates. These values are comparable to
those reported by Zaidul et al. [23] who obtained free fatty
acid and acid value during incorporated Palm kernel oil with
cocoa butter, they found most of the blend similar values to
that of cocoa butter. On the other hand, Manaf et al. [24]
found that the FFA values of rambutan seed fat and cocoa
butter they studied were 6.1±2.33% and 1.44±0.42%,
respectively. The presence of the FFA content of the cocoa
butter due to the use of beans from diseased pods or
hydrolysis by lipase from mold contamination. These molds
can be present due to insufficient drying, extended
fermentation or prolonged storage of the beans [25]. In
addition, the increase in FFA and A.V values in the roasted
seed fat could be contributed by hydrolysis of triacylglycerol
during roasting process which produces free fatty acids with
diacylglycerol. Another cause can be too quick drying of the
beans, leading to lack or inadequate loss of volatile acids,
but also hydrolysis occurring during storage can lead to FFA
formation [26].
The free fatty acid liberated from triglycerides in the other
mixtures, such as M3 (4.89±0.81%), M4 (6.49±0.00%) and
RSF (6.86±0.16%) were higher as compared to CB
(2.72±0.65%), M1 (3.01±0.32%) and M2 (3.47±0.16%) (Fig.
3). The variation of the free fatty acid due to differences in
the proportion of the mixture's component of cocoa butter
and rambutan seed fat. The result showed that rambutan
seed fat contains a higher proportion of oleic acid than that
observed in cocoa butter. Therefore, we can exhibit that M3,
M4 and RSF had the highest ratio of rambutan seed fat and
free fatty acid, respectively.
Fig. 3 Analysis of free fatty acid (FFA) of RSF and its mixture with CB
Fig. 4 Analysis of acid value (A.V) of RSF and its mixture with CB
With regard acid value (Fig. 4), high acid value was found
in sample RSF (13.66±0.23) and M4 (12.91±0.00) followed
by M3 (9.73±1.6) and M2 (5.98±0.64) mgKOH/g, whereas a
low acid value was found in the samples CB (4.68±1.29) and
M1 (5.98±0.64) mgKOH/g, respectively. From our results,
the proportion of monounsaturated fatty acid (MUFA) in
rambutan seed fat was (42.46%) significantly higher than
found in cocoa butter (22.44%). That can be explained the
61

highest value of the acid value in rambutan seed fat in
comparison with cocoa butter.
IV. CONCLUSIONS
Our analysis on texture properties, thermal stability, and
viscosity of the mixtures between fermented-roasted
rambutan seed fat and cocoa butter resulted in a conclusion
that the incorporation between RSF and CB may potentially
be applied. The hardnesses of the mixtures were lower
ranged from 11.18 to 24.77 in M3, M4 and RSF compared to
57.55 to 63.85 in M1 and CB. The thermal stability of
fermented-roasted RSF was lower than M1 and CB. The
degradation point exhibited in M1 ranged from 344.39-
521.14˚C and 394.59-616.06 in CB compared to 291.91-
482.83 in RSF. Effect of different temperature on the
viscosity of CB and M1 shows significant differences in
comparison with other mixtures. The results exhibited that
CB and M1 had a lower viscosity than M2, M3, M4 and RSF
with increasing temperature. From these results, it was found
that it is possible to utilize rambutan seed fat as a cocoa
butter replacer which allows the mixing with cocoa butter in
small ratio or can also be utilized for other confectionery
product in the absence of cocoa butter.
ACKNOWLEDGMENT
We extend our appreciation to the school of Industrial
Technology, Department of Food Technology, University
Sains Malaysia for funding the work and their keen interest
in accomplishing this work.
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